As one of inkjet printing apparatuses, a pit-in system printing apparatus has been provided which comprises at least an inkjet head, a sub tank for supplying ink to the inkjet head, and a main tank for supplying ink to the sub tank. When printing is made on a printing medium such as paper and a card by such a pit-in system printing apparatus, the inkjet head ejects ink while it moves in a direction (main scanning direction) perpendicular to a feeding direction (sub-scanning direction) of the printing medium. Furthermore, the sub tank is periodically connected to the main tank to supply ink from the main tank to the sub tank.
The inkjet head and the sub tank are integrally formed into one body and mounted on a carriage moving in the main scanning direction. On the other hand, the main tank is housed in an inkjet printing apparatus in the form of an exchangeable ink cartridge, and a connecting member is provided with the main tank for connecting to the sub tank provided in the inkjet head.
When the sub tank is replenished with ink from the ink cartridge (main tank), the sub tank is moved together with the inkjet head as well as the cartridge to a predetermined position facing the ink cartridge (main tank), and then the sub tank is connected to the ink cartridge by the connecting member, thereby replenishing the sub tank with ink.
Such a pit-in system particularly requires a mechanism for replenishing the sub tank with a predetermined amount of ink in just proportion. Therefore, the ink cartridge and the sub tank must be connected by the connecting members without fail. Furthermore, since the sub tank is replenished with ink in plurality of times with consumption of the ink in the sub tank, it is important for the connecting member to have reliability over ink leakage and durability. To improve the reliability over connection, accuracy in alignment of the sub tank with ink cartridge must be improved.
For example, Japanese Patent Laid Open No. 6-8463 describes the structure of the connecting section between the inkjet head and the ink cartridge of an inkjet printing apparatus. According to the description, the inkjet head is equipped with a liquid supply needle serving as an ink receiving section; at the same time, the ink cartridge is equipped with a connecting member serving as a joint section for supplying ink. The ink cartridge described in Japanese Patent Laid Open No. 6-8463 is shown in FIGS. 8 to 10.
As shown in these figures, the ink cartridge has a rectangular ink cartridge container 51 and a plurality of ink bags 52. The inner space of the ink cartridge container 51 is partitioned longitudinally into a plurality of spaces. The plurality of spaces partitioned each house an ink bag 52. In the end surface of the ink cartridge container 51, a plurality of ink deriving sections 53 for deriving ink 54 are provided correspondingly to the ink bags 52.
In each of the ink deriving sections 53, a connectable member 56 to an ink supply pipe 55 from the printing apparatus and a receiving portion 58 receivable for an aligning pin 57 of the printing apparatus are provided. The ink supply pipe 55 is connected to an inkjet head (not shown).
The ink cartridge container 51 is provided along a guide rail 59 of the printing apparatus. To a pipe fixing table 61 of the printing apparatus, the ink supply pipes 55 and the aligning pins 57 are fixed. When the ink cartridge container 51 is installed, the ink supply pipes 55 each pass through the connecting member 56 and enter the ink bag 52. In the stage where the ink supply pipe 55 is connected to the connecting member 56, the aligning pin 57 is fitted in the receiving portion 58, thereby aligning the connecting member 56 so as to face the ink supply pipe 55. During the aligning time, the ink deriding section 53, which is a joint section with the ink supply pipe 55, must be slid in the direction indicated by the double headed arrow in FIG. 10. Therefore, the ink deriving section 53 is held with a gap 60 interposed between the section 53 and the periphery.
Thus, when the inkjet head and the ink cartridge are connected, they are aligned with each other by sliding the ink deriving section 53 (joint section). As is apparent from FIG. 8, a plurality of ink deriving sections 53 are arranged at substantially the same intervals and distributed uniformly from the center of the ink cartridge.
In the ink cartridge described in Japanese Patent Laid Open No. 6-8463, such a connecting section is constructed on the assumption that the user may generally perform connection and disconnection of the ink cartridge for exchange one to few times.
However, in the pit-in ink system where ink is supplied as mentioned above, the sub tank provided to the inkjet head is replenished with ink a plurality of times as ink is consumed by the inkjet head. The replenishment may be performed several tens to several hundreds of times as the ink cartridge increases in volume. Every time the sub tank is replenished with ink, the inkjet head equipped with the sub tank and the ink cartridge has to be connected repeatedly. If the connection is made one to several times, the connecting member 56 such as a rubber cap, is not so significantly damaged, so that leakage of ink from a flaw formed in the connecting member 56 or due to breakage of a slit may not conceivably occur.
However, when the ink cartridge and inkjet head are connected repeatedly several tens to several hundreds of times, a flaw may be generated in the connecting member 56 and the slit of the connecting member 56 may be broken. The flaw and breakage of the connecting member 56 may cause leakage of ink from the slit of the connecting member 56 even though the ink supply pipe 55 serving as a liquid supply needle is inserted or not.
A general inkjet printing apparatus widely in use ejects ink drops of various colors from a plurality of inkjet heads so as to overlap them on a printing medium to print a color image on the medium. In general, when a color image is printed, three color inks such as yellow (Y), magenta (M), and cyan (C), or four color inks including black ink (Bk) besides these three inks are used. To correspond to these three or four color inks, three or four types of inkjet heads and ink cartridges are used. Recently, an inkjet printing apparatus having three or four types of inkjet heads installed therein for printing a full color image has been put into practical use. Furthermore, an inkjet printing apparatus capable of printing an image with high color reproducibility by using six color inks including light magenta and light cyan inks, or red and blue inks in addition to the four color inks is also put into practical use.
The ink cartridge of such an inkjet printing apparatus has a plurality of ink containers within the device for storing a plurality of inks separately. In both of such ink cartridge and sub tank provided to the inkjet heads, a plurality of connecting sections corresponding to individual ink colors are simultaneously connected.
When the inkjet head equipped with sub tank and ink cartridge are connected, if the accuracy of aligning is poor, the durability of the connecting section decreases. In particular, when connection is repeated for numerous times, leakage of ink may take place and pollute the user's hand as well as the interior space of the printing apparatus.